Methods and apparatus for constructing polar codes

ABSTRACT

Methods and apparatus for constructing polar codes are provided. A transmitter determines at least one set of parameters corresponding to data to be transmitted, and a set of sorting indices corresponding to bits of the data to be transmitted based on the set of parameters, the set of sorting indices indicating a position set of the bits to be transmitted. The transmitter polar encodes the data based at least on the set of parameters and the set of sorting indices to generate a coded block of the data, and transmits the coded block of the data.

CROSS-REFERENCE TO RELATED APPLICATION & PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.17/443,992, filed Jul. 29, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/320,038, filed Jan. 23, 2019, which issued asU.S. Pat. No. 11,128,316 on Sep. 21, 2021, which is a national stageapplication, filed under 35 U.S.C. § 371, of International PatentApplication No. PCT/CN2017/089977, filed on Jun. 26, 2017, which claimsforeign priority to International Patent Application No.PCT/CN2016/091592, filed Jul. 25, 2016, all of which are incorporated byreference herein in their entirety.

FIELD

The present disclosure relates generally to wireless communication, andmore particularly, to methods and apparatus for constructing polarcodes.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is Long Term Evolution (LTE).LTE/LTE-Advanced is a set of enhancements to the Universal MobileTelecommunications System (UMTS) mobile standard promulgated by ThirdGeneration Partnership Project (3GPP). It is designed to better supportmobile broadband Internet access by improving spectral efficiency, lowercosts, improve services, make use of new spectrum, and better integratewith other open standards using OFDMA on the downlink (DL), SC-FDMA onthe uplink (UL), and multiple-input multiple-output (MIMO) antennatechnology. However, as the demand for mobile broadband access continuesto increase, there exists a need for further improvements in LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

Block codes, or error correcting codes are frequently used to providereliable transmission of digital messages over noisy channels. In atypical block code, an information message or sequence is split up intoblocks, and an encoder at the transmitting device then mathematicallyadds redundancy to the information message. Exploitation of thisredundancy in the encoded information message is the key to reliabilityof the message, enabling correction for any bit errors that may occurdue to the noise. That is, a decoder at the receiving device can takeadvantage of the redundancy to reliably recover the information messageeven though bit errors may occur, in part, due to the addition of noiseto the channel.

Many examples of such error correcting block codes are known to those ofordinary skill in the art, including Hamming codes,Bose-Chaudhuri-Hocquenghem (BCH) codes, turbo codes, and low-densityparity check (LDPC) codes, among others. Many existing wirelesscommunication networks utilize such block codes, such as 3GPP LTEnetworks, which utilize turbo codes; and IEEE 802.11n Wi-Fi networks,which utilize LDPC codes. However, for future networks, a new categoryof block codes, called polar codes, presents a potential opportunity forreliable and efficient information transfer with improved performancerelative to turbo codes and LDPC codes.

While research into implementation of polar codes continues to rapidlyadvance its capabilities and potential, additional enhancements aredesired, particularly for potential deployment of future wirelesscommunication networks beyond LTE.

SUMMARY

Certain aspects of the present disclosure provide a method forconstructing a polar code by a transmitter. The method generallyincludes determining at least one set of parameters corresponding todata to be transmitted, and a set of sorting indices corresponding tobits of the data to be transmitted based on the set of parameters, theset of sorting indices indicating a position set of the bits to betransmitted, polar encoding the data based at least on the set ofparameters and the set of sorting indices to generate a coded block ofthe data, and transmitting the coded block of the data.

Certain aspects of the present disclosure provide a method for decodinga polar code by a receiver. The method generally includes receiving acoded block of data generated by polar encoding, determining at leastone set of parameters corresponding to the data, and a set of sortingindices corresponding to bits of the data based on the set ofparameters, the set of sorting indices indicating a position set of thebits of the data, and decoding the received coded block of data based atleast on the set of parameters and the set of sorting indices to obtaindecoded data.

Certain aspects of the present disclosure provide an apparatus forconstructing a polar code by a transmitter. The apparatus generallyincludes at least one processor and a memory coupled to the at least oneprocessor. The at least one processor is generally configured todetermine at least one set of parameters corresponding to data to betransmitted, and a set of sorting indices corresponding to bits of thedata to be transmitted based on the set of parameters, the set ofsorting indices indicating a position set of the bits to be transmitted,polar encode the data based at least on the set of parameters and theset of sorting indices to generate a coded block of the data, andtransmit the coded block of the data.

Certain aspects of the present disclosure provide an apparatus fordecoding a polar code by a receiver. The apparatus generally includes atleast one processor and a memory coupled to the at least one processor.The at least one processor is generally configured to receive a codedblock of data generated by polar encoding, determine at least one set ofparameters corresponding to the data, and a set of sorting indicescorresponding to bits of the data based on the set of parameters, theset of sorting indices indicating a position set of the bits of thedata, and decode the received coded block of data based at least on theset of parameters and the set of sorting indices to obtain decoded da.

Aspects generally include methods, apparatus, systems, computer programproducts, computer-readable medium, and processing systems, assubstantially described herein with reference to and as illustrated bythe accompanying drawings. “LTE” refers generally to LTE, LTE-Advanced(LTE-A), LTE in an unlicensed spectrum (LTE-whitespace), etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture.

FIG. 2 is a diagram illustrating an example of an access network.

FIG. 3 is a diagram illustrating an example of a DL frame structure inLTE.

FIG. 4 is a diagram illustrating an example of an UL frame structure inLTE.

FIG. 5 is a diagram illustrating an example of a radio protocolarchitecture for the user and control plane.

FIG. 6 is a diagram illustrating an example of an evolved Node B anduser equipment in an access network, in accordance with certain aspectsof the disclosure.

FIG. 7 is a schematic illustration of wireless communication between afirst wireless communication device 702 and a second wirelesscommunication device 704.

FIG. 8 is a block diagram illustrating an example of a hardwareimplementation for a wireless communication device 800 employing aprocessing system 814.

FIG. 9 illustrates example operations 900 performed by a transmitter(e.g., UE, eNB or any other network node or element thereof) forefficient construction of polar codes, in accordance with certainaspects of the present disclosure.

FIG. 10 illustrates example operations 1000 performed by a receiver(e.g., UE, eNB or any other network node or element thereof) forefficient construction of polar codes, in accordance with certainaspects of the present disclosure.

FIG. 11 illustrates an example 1100 of code construction for Polar codesfor a traffic channel, in accordance with certain aspects of the presentdisclosure.

FIG. 12 illustrates an example 1200 of code construction for Polar codesfor a traffic channel, in accordance with certain aspects of the presentdisclosure.

DETAILED DESCRIPTION

Polar codes are the first codes with an explicit construction toprovably achieve the channel capacity for symmetric binary-inputdiscrete memoryless channels. To construct Polar codes, the rows of theHadamard matrices corresponding to the good channels are selected forinformation bits. The bad channels are used for frozen bits with fixedvalue of zeros. In a practical system, density evolution or Gaussianapproximation is generally used to determine the bit-error probabilityof each channel. For example, if N information bits are desired, thebest N channels (with low error probability) are selected forinformation bits while the remaining channels are designated as frozenbits. In general, the bit-error probabilities of all the channels aresorted to determine the best and worst channels, and a position of eachbit channel is identified by a corresponding sorting index. Thus, thesorting indices of the bit channels are generally needed in order toconstruct polar codes.

To support different block sizes with different rates, differentposition sets for information bits are required indicating differentpossibilities for positions of the information bits. In addition, to getan optimum code construction, the position sets for information bits maybe different even for the same block size with different rates. In somecases, a Binary vector with 0s for positions of frozen bits and 1s forpositions of information bits, may be used to represent the position setfor information bits. However, a very large memory may be needed tostore the vector for indication of the positions of information bits.

Certain aspects of the present disclosure discuss techniques forconstructing polar codes including dynamically generating (e.g., “on thefly”) vectors or sorting indices indicating position sets of informationbits for the construction, instead of storing pre-defined vectors inmemory, thus saving memory and leading to a more efficient constructionof polar codes for both traffic and control channels.

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well-known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, modules, components,circuits, steps, processes, algorithms, etc. (collectively referred toas “elements”). These elements may be implemented using hardware,software, or combinations thereof. Whether such elements are implementedas hardware or software depends upon the particular application anddesign constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented with a “processing system”that includes one or more processors. Examples of processors includemicroprocessors, microcontrollers, digital signal processors (DSPs),field programmable gate arrays (FPGAs), programmable logic devices(PLDs), state machines, gated logic, discrete hardware circuits, andother suitable hardware configured to perform the various functionalitydescribed throughout this disclosure. One or more processors in theprocessing system may execute software. Software shall be construedbroadly to mean instructions, instruction sets, code, code segments,program code, programs, subprograms, software modules, applications,software applications, software packages, firmware, routines,subroutines, objects, executables, threads of execution, procedures,functions, etc., whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise.

Accordingly, in one or more exemplary embodiments, the functionsdescribed may be implemented in hardware, software, or combinationsthereof. If implemented in software, the functions may be stored on orencoded as one or more instructions or code on a computer-readablemedium. Computer-readable media includes computer storage media. Storagemedia may be any available media that can be accessed by a computer. Byway of example, and not limitation, such computer-readable media cancomprise RAM, ROM, EEPROM, PCM (phase change memory), flash memory,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, includes compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk and Blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim. The word “exemplary”is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

The techniques described herein may be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), CDMA2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). CDMA2000 covers IS-2000, IS-95, and IS-856standards. A TDMA network may implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). Long TermEvolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA,GSM, UMTS, and LTE are described in documents from an organization named“3rd Generation Partnership Project” (3GPP). CDMA2000 is described indocuments from an organization named “3rd Generation Partnership Project2” (3GPP2). These communications networks are merely listed as examplesof networks in which the techniques described in this disclosure may beapplied; however, this disclosure is not limited to the above-describedcommunications network.

Single carrier frequency division multiple access (SC-FDMA) is atransmission technique that utilizes single carrier modulation at atransmitter side and frequency domain equalization at a receiver side.The SC-FDMA has similar performance and essentially the same overallcomplexity as those of OFDMA system. However, SC-FDMA signal has lowerpeak-to-average power ratio (PAPR) because of its inherent singlecarrier structure. The SC-FDMA has drawn attention, especially in theuplink (UL) communications where lower PAPR greatly benefits thewireless node in terms of transmit power efficiency.

An access point (“AP”) may comprise, be implemented as, or known asNodeB, Radio Network Controller (“RNC”), eNodeB (eNB), Base StationController (“BSC”), Base Transceiver Station (“BTS”), Base Station(“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver,Basic Service Set (“BSS”), Extended Service Set (“ESS”), Radio BaseStation (“RB S”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or be knownas an access terminal, a subscriber station, a subscriber unit, a mobilestation, a remote station, a remote terminal, a user terminal, a useragent, a user device, user equipment (UE), a user station, a wirelessnode, or some other terminology. In some implementations, an accessterminal may comprise a cellular telephone, a smart phone, a cordlesstelephone, a Session Initiation Protocol (“SIP”) phone, a wireless localloop (“WLL”) station, a personal digital assistant (“PDA”), a tablet, anetbook, a smartbook, an ultrabook, a handheld device having wirelessconnection capability, a Station (“STA”), or some other suitableprocessing device connected to a wireless modem. Accordingly, one ormore aspects taught herein may be incorporated into a phone (e.g., acellular phone, a smart phone), a computer (e.g., a desktop), a portablecommunication device, a portable computing device (e.g., a laptop, apersonal data assistant, a tablet, a netbook, a smartbook, anultrabook), wearable device (e.g., smart watch, smart glasses, smartbracelet, smart wristband, smart ring, smart clothing, etc.), medicaldevices or equipment, biometric sensors/devices, an entertainment device(e.g., music device, video device, satellite radio, gaming device,etc.), a vehicular component or sensor, smart meters/sensors, industrialmanufacturing equipment, a global positioning system device, or anyother suitable device that is configured to communicate via a wirelessor wired medium. In some aspects, the node is a wireless node. Awireless node may provide, for example, connectivity for or to a network(e.g., a wide area network such as the Internet or a cellular network)via a wired or wireless communication link. Some UEs may be consideredmachine-type communication (MTC) UEs, which may include remote devices,that may communicate with a base station, another remote device, or someother entity. Machine type communications (MTC) may refer tocommunication involving at least one remote device on at least one endof the communication and may include forms of data communication whichinvolve one or more entities that do not necessarily need humaninteraction. MTC UEs may include UEs that are capable of MTCcommunications with MTC servers and/or other MTC devices through PublicLand Mobile Networks (PLMN), for example. Examples of MTC devicesinclude sensors, meters, location tags, monitors, drones, robots/roboticdevices, etc. MTC UEs, as well as other types of UEs, may be implementedas NB-IoT (narrowband internet of things) devices.

FIG. 1 is a diagram illustrating an LTE network architecture 100 inwhich aspects of the present disclosure may be practiced.

In certain aspects, a transmitter (e.g., UE 102 or eNB 106) determinesat least one set of parameters corresponding to data to be transmitted,and a set of sorting indices corresponding to bits of the data to betransmitted based on the set of parameters, the set of sorting indicesindicating a position set of the bits to be transmitted. The transmitterpolar encodes the data based at least on the set of parameters and theset of sorting indices to generate a coded block of the data. Thetransmitter then transmits the coded block of the data.

In certain aspects, a receiver (e.g., UE 102 or eNB 106) receives acoded block of data generated by polar encoding. The receiver determinesat least one set of parameters corresponding to the data, and a set ofsorting indices corresponding to bits of the data based on the set ofparameters, the set of sorting indices indicating a position set of thebits of the data. The receiver then decodes the received coded block ofdata based at least on the set of parameters and the set of sortingindices to obtain decoded data.

The LTE network architecture 100 may be referred to as an Evolved PacketSystem (EPS) 100. The EPS 100 may include one or more user equipment(UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS)120, and an Operator's IP Services 122. The EPS can interconnect withother access networks, but for simplicity those entities/interfaces arenot shown. Exemplary other access networks may include an IP MultimediaSubsystem (IMS) PDN, Internet PDN, Administrative PDN (e.g.,Provisioning PDN), carrier-specific PDN, operator-specific PDN, and/orGPS PDN. As shown, the EPS provides packet-switched services, however,as those skilled in the art will readily appreciate, the variousconcepts presented throughout this disclosure may be extended tonetworks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108.The eNB 106 provides user and control plane protocol terminations towardthe UE 102. The eNB 106 may be connected to the other eNBs 108 via an X2interface (e.g., backhaul). The eNB 106 may also be referred to as abase station, a base transceiver station, a radio base station, a radiotransceiver, a transceiver function, a basic service set (BSS), anextended service set (ESS), an access point, or some other suitableterminology. The eNB 106 may provide an access point to the EPC 110 fora UE 102. Examples of UEs 102 include a cellular phone, a smart phone, asession initiation protocol (SIP) phone, a laptop, a personal digitalassistant (PDA), a satellite radio, a global positioning system, amultimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, a tablet, a netbook, a smart book, anultrabook, a drone, a robot, a sensor, a monitor, a meter, acamera/security camera, a gaming device, a wearable device (e.g., smartwatch, smart glasses, smart ring, smart bracelet, smart wrist band,smart jewelry, smart clothing, etc.), any other similar functioningdevice, etc. The UE 102 may also be referred to by those skilled in theart as a mobile station, a subscriber station, a mobile unit, asubscriber unit, a wireless unit, a remote unit, a mobile device, awireless device, a wireless communications device, a remote device, amobile subscriber station, an access terminal, a mobile terminal, awireless terminal, a remote terminal, a handset, a user agent, a mobileclient, a client, or some other suitable terminology.

The eNB 106 is connected by an S1 interface to the EPC 110. The EPC 110includes a Mobility Management Entity (MME) 112, other MMES 114, aServing Gateway 116, and a Packet Data Network (PDN) Gateway 118. TheMME 112 is the control node that processes the signaling between the UE102 and the EPC 110. Generally, the MME 112 provides bearer andconnection management. All user IP packets are transferred through theServing Gateway 116, which itself is connected to the PDN Gateway 118.The PDN Gateway 118 provides UE IP address allocation as well as otherfunctions. The PDN Gateway 118 is connected to the Operator's IPServices 122. The Operator's IP Services 122 may include, for example,the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS(packet-switched) Streaming Service (PSS). In this manner, the UE102 maybe coupled to the PDN through the LTE network.

FIG. 2 is a diagram illustrating an example of an access network 200 inan LTE network architecture in which aspects of the present disclosuremay be practiced. For example, UEs 206 and eNBs 204 may be configured toimplement techniques for efficient construction of polar codes inaccordance with aspects of the present disclosure.

In this example, the access network 200 is divided into a number ofcellular regions (cells) 202. One or more lower power class eNBs 208 mayhave cellular regions 210 that overlap with one or more of the cells202. A lower power class eNB 208 may be referred to as a remote radiohead (RRH). The lower power class eNB 208 may be a femto cell (e.g.,home eNB (HeNB)), pico cell, or micro cell. The macro eNBs 204 are eachassigned to a respective cell 202 and are configured to provide anaccess point to the EPC 110 for all the UEs 206 in the cells 202. Thereis no centralized controller in this example of an access network 200,but a centralized controller may be used in alternative configurations.The eNBs 204 are responsible for all radio related functions includingradio bearer control, admission control, mobility control, scheduling,security, and connectivity to the serving gateway 116. The network 200may also include one or more relays (not shown). According to oneapplication, a UE may serve as a relay.

The modulation and multiple access scheme employed by the access network200 may vary depending on the particular telecommunications standardbeing deployed. In LTE applications, OFDM is used on the DL and SC-FDMAis used on the UL to support both frequency division duplexing (FDD) andtime division duplexing (TDD). As those skilled in the art will readilyappreciate from the detailed description to follow, the various conceptspresented herein are well suited for LTE applications. However, theseconcepts may be readily extended to other telecommunication standardsemploying other modulation and multiple access techniques. By way ofexample, these concepts may be extended to Evolution-Data Optimized(EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interfacestandards promulgated by the 3rd Generation Partnership Project 2(3GPP2) as part of the CDMA2000 family of standards and employs CDMA toprovide broadband Internet access to mobile stations. These concepts mayalso be extended to Universal Terrestrial Radio Access (UTRA) employingWideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA;Global System for Mobile Communications (GSM) employing TDMA; andEvolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employingOFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents fromthe 3GPP organization. CDMA2000 and UMB are described in documents fromthe 3GPP2 organization. The actual wireless communication standard andthe multiple access technology employed will depend on the specificapplication and the overall design constraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. Theuse of MIMO technology enables the eNBs 204 to exploit the spatialdomain to support spatial multiplexing, beamforming, and transmitdiversity. Spatial multiplexing may be used to transmit differentstreams of data simultaneously on the same frequency. The data streamsmay be transmitted to a single UE 206 to increase the data rate or tomultiple UEs 206 to increase the overall system capacity. This isachieved by spatially precoding each data stream (e.g., applying ascaling of an amplitude and a phase) and then transmitting eachspatially precoded stream through multiple transmit antennas on the DL.The spatially precoded data streams arrive at the UE(s) 206 withdifferent spatial signatures, which enables each of the UE(s) 206 torecover the one or more data streams destined for that UE 206. On theUL, each UE 206 transmits a spatially precoded data stream, whichenables the eNB 204 to identify the source of each spatially precodeddata stream.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas. To achieve good coverage at the edges of the cell, asingle stream beamforming transmission may be used in combination withtransmit diversity.

In the detailed description that follows, various aspects of an accessnetwork may be described with reference to a MIMO system supporting OFDMon the DL. OFDM is a spread-spectrum technique that modulates data overa number of subcarriers within an OFDM symbol. The subcarriers arespaced apart at precise frequencies. The spacing provides“orthogonality” that enables a receiver to recover the data from thesubcarriers. In the time domain, a guard interval (e.g., cyclic prefix)may be added to each OFDM symbol to combat inter-OFDM-symbolinterference. The UL may use SC-FDMA in the form of a DFT-spread OFDMsignal to compensate for high peak-to-average power ratio (PAPR).

FIG. 3 is a diagram 300 illustrating an example of a DL frame structurein LTE. A frame (10 ms) may be divided into 10 equally sized sub-frameswith indices of 0 through 9. Each sub-frame may include two consecutivetime slots. A resource grid may be used to represent two time slots,each time slot including a resource block. The resource grid is dividedinto multiple resource elements. In LTE, a resource block contains 12consecutive subcarriers in the frequency domain and, for a normal cyclicprefix in each OFDM symbol, 7 consecutive OFDM symbols in the timedomain, or 84 resource elements. For an extended cyclic prefix, aresource block contains 6 consecutive OFDM symbols in the time domainand has 72 resource elements. Some of the resource elements, asindicated as R 302, R 304, include DL reference signals (DL-RS). TheDL-RS include Cell-specific RS (CRS) (also sometimes called common RS)302 and UE-specific RS (UE-RS) 304. UE-RS 304 are transmitted only onthe resource blocks upon which the corresponding physical DL sharedchannel (PDSCH) is mapped. The number of bits carried by each resourceelement depends on the modulation scheme. Thus, the more resource blocksthat a UE receives and the higher the modulation scheme, the higher thedata rate for the UE.

In LTE, an eNB may send a primary synchronization signal (PSS) and asecondary synchronization signal (SSS) for each cell in the eNB. Theprimary and secondary synchronization signals may be sent in symbolperiods 6 and 5, respectively, in each of subframes 0 and 5 of eachradio frame with the normal cyclic prefix (CP). The synchronizationsignals may be used by UEs for cell detection and acquisition. The eNBmay send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 inslot 1 of subframe 0. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) inthe first symbol period of each subframe. The PCFICH may convey thenumber of symbol periods (M) used for control channels, where M may beequal to 1, 2 or 3 and may change from subframe to subframe. M may alsobe equal to 4 for a small system bandwidth, e.g., with less than 10resource blocks. The eNB may send a Physical HARQ Indicator Channel(PHICH) and a Physical Downlink Control Channel (PDCCH) in the first Msymbol periods of each subframe. The PHICH may carry information tosupport hybrid automatic repeat request (HARQ). The PDCCH may carryinformation on resource allocation for UEs and control information fordownlink channels. The eNB may send a Physical Downlink Shared Channel(PDSCH) in the remaining symbol periods of each subframe. The PDSCH maycarry data for UEs scheduled for data transmission on the downlink.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNB. The eNB may send the PCFICH and PHICHacross the entire system bandwidth in each symbol period in which thesechannels are sent. The eNB may send the PDCCH to groups of UEs incertain portions of the system bandwidth. The eNB may send the PDSCH tospecific UEs in specific portions of the system bandwidth. The eNB maysend the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to allUEs, may send the PDCCH in a unicast manner to specific UEs, and mayalso send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element (RE) may cover one subcarrier in one symbol periodand may be used to send one modulation symbol, which may be a real orcomplex value. Resource elements not used for a reference signal in eachsymbol period may be arranged into resource element groups (REGs). EachREG may include four resource elements in one symbol period. The PCFICHmay occupy four REGs, which may be spaced approximately equally acrossfrequency, in symbol period 0. The PHICH may occupy three REGs, whichmay be spread across frequency, in one or more configurable symbolperiods. For example, the three REGs for the PHICH may all belong insymbol period 0 or may be spread in symbol periods 0, 1, and 2. ThePDCCH may occupy 9, 18, 36, or 72 REGs, which may be selected from theavailable REGs, in the first M symbol periods, for example. Only certaincombinations of REGs may be allowed for the PDCCH. In aspects of thepresent methods and apparatus, a subframe may include more than onePDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for the PDCCH. An eNB may send the PDCCH to the UE in anyof the combinations that the UE will search.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structurein LTE. The available resource blocks for the UL may be partitioned intoa data section and a control section. The control section may be formedat the two edges of the system bandwidth and may have a configurablesize. The resource blocks in the control section may be assigned to UEsfor transmission of control information. The data section may includeall resource blocks not included in the control section. The UL framestructure results in the data section including contiguous subcarriers,which may allow a single UE to be assigned all of the contiguoussubcarriers in the data section.

A UE may be assigned resource blocks 410 a, 410 b in the control sectionto transmit control information to an eNB. The UE may also be assignedresource blocks 420 a, 420 b in the data section to transmit data to theeNB. The UE may transmit control information in a physical UL controlchannel (PUCCH) on the assigned resource blocks in the control section.The UE may transmit only data or both data and control information in aphysical UL shared channel (PUSCH) on the assigned resource blocks inthe data section. A UL transmission may span both slots of a subframeand may hop across frequency.

A set of resource blocks may be used to perform initial system accessand achieve UL synchronization in a physical random access channel(PRACH) 430. The PRACH 430 carries a random sequence and cannot carryany UL data/signaling. Each random access preamble occupies a bandwidthcorresponding to six consecutive resource blocks. The starting frequencyis specified by the network. That is, the transmission of the randomaccess preamble is restricted to certain time and frequency resources.There is no frequency hopping for the PRACH. The PRACH attempt iscarried in a single subframe (1 ms) or in a sequence of few contiguoussubframes and a UE can make only a single PRACH attempt per frame (10ms).

FIG. 5 is a diagram 500 illustrating an example of a radio protocolarchitecture for the user and control planes in LTE. The radio protocolarchitecture for the UE and the eNB is shown with three layers: Layer 1,Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer andimplements various physical layer signal processing functions. The L1layer will be referred to herein as the physical layer 506. Layer 2 (L2layer) 508 is above the physical layer 506 and is responsible for thelink between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control(MAC) sublayer 510, a radio link control (RLC) sublayer 512, and apacket data convergence protocol (PDCP) 514 sublayer, which areterminated at the eNB on the network side. Although not shown, the UEmay have several upper layers above the L2 layer 508 including a networklayer (e.g., IP layer) that is terminated at the PDN gateway 118 on thenetwork side, and an application layer that is terminated at the otherend of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 514 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between eNBs. The RLC sublayer 512 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ). The MACsublayer 510 provides multiplexing between logical and transportchannels. The MAC sublayer 510 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNBis substantially the same for the physical layer 506 and the L2 layer508 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 516 in Layer 3 (L3 layer). The RRC sublayer 516is responsible for obtaining radio resources (i.e., radio bearers) andfor configuring the lower layers using RRC signaling between the eNB andthe UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650in an access network, in which aspects of the present disclosure may bepracticed.

In certain aspects, a transmitter (e.g., UE 650 or eNB 610) determinesat least one set of parameters corresponding to data to be transmitted,and a set of sorting indices corresponding to bits of the data to betransmitted based on the set of parameters, the set of sorting indicesindicating a position set of the bits to be transmitted. The transmitterpolar encodes the data based at least on the set of parameters and theset of sorting indices to generate a coded block of the data. Thetransmitter then transmits the coded block of the data.

In certain aspects, a receiver (e.g., UE 650 or eNB 610) receives acoded block of data generated by polar encoding. The receiver determinesat least one set of parameters corresponding to the data, and a set ofsorting indices corresponding to bits of the data based on the set ofparameters, the set of sorting indices indicating a position set of thebits of the data. The receiver then decodes the received coded block ofdata based at least on the set of parameters and the set of sortingindices to obtain decoded data.

In the DL, upper layer packets from the core network are provided to acontroller/processor 675. The controller/processor 675 implements thefunctionality of the L2 layer. In the DL, the controller/processor 675provides header compression, ciphering, packet segmentation andreordering, multiplexing between logical and transport channels, andradio resource allocations to the UE 650 based on various prioritymetrics. The controller/processor 675 is also responsible for HARQoperations, retransmission of lost packets, and signaling to the UE 650.

The TX processor 616 implements various signal processing functions forthe L1 layer (i.e., physical layer). The signal processing functionsincludes coding and interleaving to facilitate forward error correction(FEC) at the UE 650 and mapping to signal constellations based onvarious modulation schemes (e.g., binary phase-shift keying (BPSK),quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK),M-quadrature amplitude modulation (M-QAM)). The coded and modulatedsymbols are then split into parallel streams. Each stream is then mappedto an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot)in the time and/or frequency domain, and then combined together using anInverse Fast Fourier Transform (IFFT) to produce a physical channelcarrying a time domain OFDM symbol stream. The OFDM stream is spatiallyprecoded to produce multiple spatial streams. Channel estimates from achannel estimator 674 may be used to determine the coding and modulationscheme, as well as for spatial processing. The channel estimate may bederived from a reference signal and/or channel condition feedbacktransmitted by the UE 650. Each spatial stream is then provided to adifferent antenna 620 via a separate transmitter 618TX. Each transmitter618TX modulates an RF carrier with a respective spatial stream fortransmission.

At the UE 650, each receiver 654RX receives a signal through itsrespective antenna 652. Each receiver 654RX recovers informationmodulated onto an RF carrier and provides the information to thereceiver (RX) processor 656. The RX processor 656 implements varioussignal processing functions of the L1 layer. The RX processor 656performs spatial processing on the information to recover any spatialstreams destined for the UE 650. If multiple spatial streams aredestined for the UE 650, they may be combined by the RX processor 656into a single OFDM symbol stream. The RX processor 656 then converts theOFDM symbol stream from the time-domain to the frequency domain using aFast Fourier Transform (FFT). The frequency domain signal comprises aseparate OFDM symbol stream for each subcarrier of the OFDM signal. Thesymbols on each subcarrier, and the reference signal, is recovered anddemodulated by determining the most likely signal constellation pointstransmitted by the eNB 610. These soft decisions may be based on channelestimates computed by the channel estimator 658. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the eNB 610 on the physical channel.The data and control signals are then provided to thecontroller/processor 659.

The controller/processor 659 implements the L2 layer. Thecontroller/processor can be associated with a memory 660 that storesprogram codes and data. The memory 660 may be referred to as acomputer-readable medium. In the UL, the controller/processor 659provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 662, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 662 for L3 processing. Thecontroller/processor 659 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets tothe controller/processor 659. The data source 667 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by the eNB 610, thecontroller/processor 659 implements the L2 layer for the user plane andthe control plane by providing header compression, ciphering, packetsegmentation and reordering, and multiplexing between logical andtransport channels based on radio resource allocations by the eNB 610.The controller/processor 659 is also responsible for HARQ operations,retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a referencesignal or feedback transmitted by the eNB 610 may be used by the TXprocessor 668 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 668 are provided to different antenna 652 via separatetransmitters 654TX. Each transmitter 654TX modulates an RF carrier witha respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar tothat described in connection with the receiver function at the UE 650.Each receiver 618RX receives a signal through its respective antenna620. Each receiver 618RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 670. The RXprocessor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. Thecontroller/processor 675 can be associated with a memory 676 that storesprogram codes and data. The memory 676 may be referred to as acomputer-readable medium. In the UL, the controller/processor 675provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the UE 650. Upper layer packets fromthe controller/processor 675 may be provided to the core network. Thecontroller/processor 675 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations. Thecontrollers/processors 675, 659 may direct the operations at the eNB 610and the UE 650, respectively.

The controller/processor 659 and/or other processors, components and/ormodules at the UE 650 and/or the controller/processor 675 and/or otherprocessors, components and/or modules at the eNB 610 may perform ordirect operations, for example, operations 900 and 1000 in FIGS. 9 and10 respectively, and/or other processes for the techniques describedherein for implementing the efficient construction of polar codes. Incertain aspects, one or more of any of the components shown in FIG. 6may be employed to perform example operations 900 and 1000, and/or otherprocesses for the techniques described herein. The memories 660 and 676may store data and program codes for the UE 650 and eNB 610respectively, accessible and executable by one or more other componentsof the UE 650 and the eNB 610.

Example Techniques for Constructing Polar Codes

FIG. 7 is a schematic illustration 700 of wireless communication betweena first wireless communication device 702 and a second wirelesscommunication device 704. In the illustrated example, the first wirelesscommunication device 702 transmits a digital message over acommunication channel 706 (e.g., a wireless channel) to the secondwireless communication device 704. One issue in such a scheme that mustbe addressed to provide for reliable communication of the digitalmessage, is to take into account the noise that affects thecommunication channel 706.

Block codes, or error correcting codes are frequently used to providereliable transmission of digital messages over such noisy channels. In atypical block code, an information message or sequence is split up intoblocks, each block having a length of K bits. An encoder 724 at thefirst (transmitting) wireless communication device 102 thenmathematically adds redundancy to the information message, resulting incodewords having a length of N, where N>K. Here, the code rate R is theratio between the message length and the block length: i.e., R=K/N.Exploitation of this redundancy in the encoded information message isthe key to reliability of the message, enabling correction for any biterrors that may occur due to the noise. That is, a decoder 742 at thesecond (receiving) wireless communication device 704 can take advantageof the redundancy to reliably recover the information message eventhough bit errors may occur, in part, due to the addition of noise tothe channel.

Many examples of such error correcting block codes are known to those ofordinary skill in the art, including Hamming codes,Bose-Chaudhuri-Hocquenghem (BCH) codes, turbo codes, and low-densityparity check (LDPC) codes, among others. Many existing wirelesscommunication networks utilize such block codes, such as 3GPP LTEnetworks, which utilize turbo codes; and IEEE 802.11n Wi-Fi networks,which utilize LDPC codes. However, for future networks, a new categoryof block codes, called polar codes, presents a potential opportunity forreliable and efficient information transfer with improved performancerelative to turbo codes and LDPC codes.

Polar codes are linear block error correcting codes invented in 2007 byErdal Arikan, and currently known to those skilled in the art. Ingeneral terms, channel polarization is generated with a recursivealgorithm that defines polar codes. Polar codes are the first explicitcodes that achieve the channel capacity of symmetric binary-inputdiscrete memoryless channels. That is, polar codes achieve the channelcapacity (the Shannon limit) or the theoretical upper bound on theamount of error-free information that can be transmitted on a discretememoryless channel of a given bandwidth in the presence of noise.

FIG. 8 is a block diagram illustrating an example of a hardwareimplementation for a wireless communication device 800 employing aprocessing system 814. In accordance with various aspects of thedisclosure, an element, or any portion of an element, or any combinationof elements may be implemented with a processing system 814 thatincludes one or more processors 804. For example, the wirelesscommunication device 800 may be a user equipment (UE), a base station,or any other suitable apparatus or means for wireless communication.Examples of processors 804 include microprocessors, microcontrollers,digital signal processors (DSPs), field programmable gate arrays(FPGAs), programmable logic devices (PLDs), state machines, gated logic,discrete hardware circuits, and other suitable hardware configured toperform the various functionality described throughout this disclosure.That is, the processor 804, as utilized in a wireless communicationdevice 800, may be used to implement any one or more of the processesdescribed below and illustrated in FIGS. 9-12 .

In this example, the processing system 814 may be implemented with a busarchitecture, represented generally by the bus 802. The bus 802 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 814 and the overall designconstraints. The bus 802 links together various circuits including oneor more processors (represented generally by the processor 804), amemory 805, and computer-readable media (represented generally by thecomputer-readable medium 806). The bus 802 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further. A bus interface 808provides an interface between the bus 802 and a transceiver 810. Thetransceiver 810 provides a means for communicating with various otherapparatus over a transmission medium. Depending upon the nature of theapparatus, a user interface 812 (e.g., keypad, display, speaker,microphone, joystick) may also be provided.

The processor 804 may include an encoder 841, which may in some examplesoperate in coordination with encoding software 861 stored in thecomputer-readable storage medium 806. Further, the processor 804 mayinclude a decoder 842, which may in some examples operate incoordination with decoding software 862 stored in the computer-readablemedium 806.

The processor 804 is responsible for managing the bus 802 and generalprocessing, including the execution of software stored on thecomputer-readable medium 806. The software, when executed by theprocessor 804, causes the processing system 814 to perform the variousfunctions described below for any particular apparatus. Thecomputer-readable medium 806 may also be used for storing data that ismanipulated by the processor 804 when executing software.

One or more processors 804 in the processing system may executesoftware. Software shall be construed broadly to mean instructions,instruction sets, code, code segments, program code, programs,subprograms, software modules, applications, software applications,software packages, routines, subroutines, objects, executables, threadsof execution, procedures, functions, etc., whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. The software may reside on a computer-readablemedium 806. The computer-readable medium 806 may be a non-transitorycomputer-readable medium. A non-transitory computer-readable mediumincludes, by way of example, a magnetic storage device (e.g., hard disk,floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD)or a digital versatile disc (DVD)), a smart card, a flash memory device(e.g., a card, a stick, or a key drive), a random access memory (RAM), aread only memory (ROM), a programmable ROM (PROM), an erasable PROM(EPROM), an electrically erasable PROM (EEPROM), a register, a removabledisk, and any other suitable medium for storing software and/orinstructions that may be accessed and read by a computer.

The computer-readable medium may also include, by way of example, acarrier wave, a transmission line, and any other suitable medium fortransmitting software and/or instructions that may be accessed and readby a computer. The computer-readable medium 806 may reside in theprocessing system 814, external to the processing system 814, ordistributed across multiple entities including the processing system814. The computer-readable medium 806 may be embodied in a computerprogram product. By way of example, a computer program product mayinclude a computer-readable medium in packaging materials.

Those skilled in the art will recognize how best to implement thedescribed functionality presented throughout this disclosure dependingon the particular application and the overall design constraints imposedon the overall system.

As noted above, Polar codes are the first codes with an explicitconstruction to provably achieve the channel capacity for symmetricbinary-input discrete memoryless channels. The capacity may be achievedwith a simple successive cancellation (SC) decoder. Polar codes and LDPCcodes are two competitive candidates for 5G channel coding.

As noted above, Polar codes are block codes. The generate matrices ofPolar codes may be submatrices of Hadamard matrices. Generally, each rowof the generate matrices corresponds to a bit-channel. To constructPolar codes, the rows of the Hadamard matrices corresponding to the goodchannels are selected for information bits. The bad channels are usedfor frozen bits with fixed value of zeros. In a practical system,density evolution or Gaussian approximation is generally used todetermine the bit-error probability of each channel. For example, if Ninformation bits are desired, the best N channels (with low errorprobability) are selected for information bits while the remainingchannels are designated as frozen bits. In general, the bit-errorprobabilities of all the channels are sorted to determine the best andworst channels, and a position of each bit channel is identified by acorresponding sorting index. Thus, the sorting indices of the bitchannels are generally needed in order to construct polar codes.

The requirement of sorting the channel quality for Polar codes isgenerally different from Turbo codes. For example, for Turbo codes, itis easy to get the code word as long as the code structure is defined.Regarding Polar codes, to support different block sizes with differentrates, different position sets for information bits are requiredindicating different possibilities for positions of the informationbits. In addition, to get an optimum code construction, the positionsets for information bits may be different even for the same block sizewith different rates.

In some cases, a Binary vector with 0s for positions of frozen bits and1s for positions of information bits, is generally a good way torepresent the position set for information bits. However, a very largememory may still be needed even if we save the vector for indication ofthe positions of information bits. For example, assuming 200 informationblock sizes are used and 10 rates are supported in a system, and that abinary vector with an average length of 1000 bits is used forrepresentation of the position sets for information bits or frozen bits,a memory of 2 million bits may be needed to store the vectors forindicating the positions of the information bits. Further, puncturingmay be used to obtain length-compatible polar codes having a variablecode word whose block length is variable. Thus, if we consider ratematching for variable block sizes, the memory required to store thevectors may be, for example, 100 times more assuming only 100 variableblock sizes are used for each rate. Thus, the memory required to storethe vectors (e.g., sorting indices) indicating the position ofinformation bits is generally very large.

Certain aspects of the present disclosure discuss techniques forconstructing polar codes including generating vectors or sorting indicesindicating position sets of information bits for the constructiondynamically (e.g., “on the fly”), instead of storing pre-defined vectorsin memory, thus saving memory and leading to a more efficientconstruction of polar codes for both traffic and control channels.

In certain aspects, a scheme of density evolution or Gaussianapproximation (GA) may be used to determine channel quality (e.g., biterror probability for each bit channel). Density evolution has beenknown to be used for construction of polar codes, and is generally knownto those skilled in the art, and therefore the details thereof are notdescribed herein. It has also been known in the art to use a lowercomplexity version of density evolution utilizing Gaussian approximation(GA) of densities, for the construction of polar codes. Gaussianapproximation is also known to those skilled in the art. Because oflower complexity, GA is widely used. Let's assume an all-zero code wordwith BPSK modulation is transmitted over Additive While Gaussian Channel(AWGN) channel. The mean and the variance of the receive Loglikelihoodratio (LLR) may be

${\frac{1}{\sigma^{2}}{and}\frac{4}{\sigma^{2}}},$

respectively. For Polar codes with length of N bits, the GA scheme maybe descripted as follows.

For example, input may be given by,

${- e_{m,i}} = \frac{2}{\sigma^{2}}$

-   -   with m=log₂ N and i=1, . . . , N    -   The e_(m,i) can be looked as the LLR of each channel at stage m.        The e_(0,j) can be looked as the initial LLR of each channel.

Proceeding may be given by,

e _(1,i)=ϕ⁻¹(1−ϕ(e _(l+1) ,i))(1−ϕ(e _(l+1,i+n))))

e _(l,i+n) =e _(l+1,i) +e _(l+1,i+n)

-   -   Where l=m, m−1, . . . , 0; i∈{2 nh+j|0≤h<2^(l),0≤j<n}n=2^(m-l-1)        and

${\phi(x)} = \left\{ \begin{matrix}{1 - {\frac{1}{4\pi x}{\int}_{- \infty}^{\infty}\tan{h\left( {z/2} \right)}e^{\frac{{({z - x})}^{2}}{4x}{dz}}}} & {x \geq 0} \\1 & {x = 0}\end{matrix} \right.$

Output of the GA scheme may be the sorting index of e_(0,i) or thevector for the indication of the positions for information bits andfrozen bits.

Thus, the output may be determined based on the noise variance and codedblock size N. Thus, in an aspect, the vector of good channel positions(or sorting indices) may be generated on the fly as long as the noisevariance and coded block size are known. In addition, the function andanti-function of ϕ(x) may be implemented by a look-up table forsimplification. In certain aspects, the algorithm shown above may bemodified to support variable blocks sizes by considering puncturepatterns.

FIG. 9 illustrates example operations 900 performed by a transmitter(e.g., UE, eNB or any other network node or element thereof) forefficient construction of polar codes, in accordance with certainaspects of the present disclosure. Operations 900 begin, at 902, bydetermining at least one set of parameters corresponding to data to betransmitted and a set of indices (e.g., sorting indices) correspondingto bits of the data to be transmitted based on the set of parameters,the set of sorting indices indicating a position set of the bits to betransmitted. At 904, the transmitter polar encodes the data based atleast on the set of parameters and the set of sorting indices togenerate a coded block of the data. At 906, the transmitter transmitsthe coded block of the data. In an aspect, the set of parametersincludes information block size K, coded block size N or constructionSNR of

$\frac{1}{\delta^{2}},$

or a combination thereof.

FIG. 10 illustrates example operations 1000 performed by a receiver(e.g., UE, eNB or any other network node or element thereof) forefficient construction of polar codes, in accordance with certainaspects of the present disclosure. Operations 1000 begin, at 1002, byreceiving a coded block of data generated by polar encoding. At 1004,the receiver determines at least one set of parameters corresponding tothe data and a set of sorting indices corresponding to bits of the data,based on the set of parameters, the set of sorting indices indicating aposition set of the bits of the data. At 1006, the receiver decodes thereceived coded block of data based at least on the set of parameters andthe set of sorting indices to obtain decoded data.

As noted above, the position set for information bits of data isnecessary for construction of Polar codes. To obtain good performance, alarge memory is needed to store the binary vectors which represent theposition set. In general, GA algorithm is widely used to generatesorting index of the channel quality or the corresponding vector. Incertain aspects, since the sorting index is determined based onparameters including the information block size K, the coded block sizeN and the construction SNR of

$\frac{1}{\delta^{2}},$

it is easy for both the transmitter and receiver to generate the sortingindices on the fly as long as the three factors are known to them. In apractical system, a device may determine the information block size Kand the coded block size N from control information known to the device.The construction SNR δ may be obtained from a pre-defined look-up, eachpair of (N, K) in the look-up table corresponding to a particular valueof the construction SNR δ.

Thus, to avoid the large memory for storing the sorting indices, aspectsof the present disclosure propose generating the sorting indices of thechannel quality or the vectors on the fly in both transmitter andreceiver.

Constructing Polar Codes for a Traffic Channel

FIG. 11 illustrates an example 1100 of code construction for Polar codesfor a traffic channel, in accordance with certain aspects of the presentdisclosure. In transmitter 1100 a, the transport block 1102 of physicaldata to be transmitted is first divided into several information blocks1104, for example, if the transport block size is larger than themaximum information block size defined for Polar codes. In an aspect,each information block 1004 has an information block size (e.g., numberof information bits) In an aspect, a size of at least one of theinformation blocks 1004 is determined as the information block sizeK_(i) for the construction of the Polar Codes. In an aspect, eachinformation block's size may be determined as the information block sizeK_(i) corresponding to the information block for construction of PolarCodes. The coded block size N_(i) of code blocks 1106 may be determined,for example, based on the amount of resources allocated for transmissionof the data. In an aspect, overhead such as reference signals is removedwhen the actual resource size is calculated. In an aspect, the codedblock size N_(i) may vary based on the allocated resource. For example,in LTE, different PRBs may have different amount of REs allocated forreference signals (RSs). These REs allocated for the RSs are generallyremoved from consideration before determining the actual resource sizefor calculating the coded block size. Different PRBs may have differentamounts of REs allocated for RSs and thus may result in different codedblock sizes.

After the information block size K_(i) and coded block size N_(i) areobtained, noise variance 1108 (e.g., construction SNR δ_(i)) is obtainedbased on the code block size N_(i) and the information block size K_(i),for example from a predefined look-up table. In an aspect, in thelook-up table, each pair of (N_(i), K_(i)) is mapped to a specific valuefor each construction SNR δ_(i) 1108. In an aspect, a value of theconstruction SNR δ_(i) is looked up from the look-up table, the value ofthe construction SNR δ_(i) in the look-up table corresponding to acombination of a value of the code block size N, and a value of theinformation block size K_(i). In an aspect, the values of theconstruction SNR δ_(i) are optimized based on N_(i) and K_(i). In anaspect, the pre-defined look-up table may be generated and a copy of thelook-up table may be stored in both the transmitter 1100 a and thereceiver 1100 b. A puncture pattern 1110 is then determined (e.g., ifpuncturing is employed). After the puncture pattern 1110 has beendetermined, the sorting index 1112 of the channel quality is obtained bythe GA algorithm using parameters set (N_(i), K_(i), δ_(i)). In thisway, the position set of each set of the information bits will bedetermined by the sorting indices. The coded blocks 1114 are obtained byPolar encoding and puncturing according to the puncture pattern.

In certain aspects, the transmitter 1100 a transmits to the receiver1100 b, control information regarding one or more of resource size, MCSlevel, or HARQ version. In the receiver 1100 b, the transport block size1102 may be deduced from the control information such as resource size,MCS level, and HARQ version received from the transmitter. After thetransport block size is known, the position of the information bits(e.g., sorting indices) is obtained by the similar procedure describedfor the transmitter. For example, the transport block 1102 is dividedinto several information blocks 1104, and the information block sizeK_(i) of information block sizes, coded block size Ni, and thepuncturing pattern 1110 is determined at the receiver by a similarprocedure employed at the transmitter. In an aspect, the same predefinedlook-up table for mapping (N_(i), K_(i)) into δ_(i) is applied for bothtransmitter and receiver. As a result, the position set of theinformation bits obtained at the transmitter is substantially identicalto that obtained at the receiver. In this way, the received signal maybe decoded correctly block by block at the receiver, for example, basedon the parameter set (N_(i), K_(i), δ_(i)) and the sorting indicesdetermined at the receiver.

Constructing Polar Codes for a Control Channel

FIG. 12 illustrates an example 1200 of code construction for Polar codesfor a traffic channel, in accordance with certain aspects of the presentdisclosure. In transmitter 1200 a, the number of the information bits(e.g., information block size K_(i) 1204) is determined by the size ofthe control data 1202. The coded block size N_(i) of code blocks 1206 isdetermined by the resource allocated and the modulation used. Theoverhead such as reference signals are removed when the actual resourcesize is calculated for determining the coded block size N_(i). After theinformation block size K_(i) and coded block size N_(i) are obtained,the noise variance 1208 (e.g., construction SNR δ_(i)) is determinedfrom the predefined look-up table. As discussed previously, in thetable, each pair of (N_(i), K_(i)) corresponds to a specific value ofconstruction SNR δ_(i). The values of the construction SNR δ_(i) areoptimized based on N_(i) and K_(i) predefined in the table. A puncturepattern 1210 is determined. After the puncture pattern 1210 has beendetermined, the sorting index 1212 of the channel quality is obtained bythe GA algorithm using parameters of (N_(i), K_(i), δ_(i)). In this way,the position set of the information bits is determined by the sortingindices 1212. The coded block 1214 is obtained by Polar encoding andpuncturing according to the puncture pattern.

In an aspect, the coded block sizes for control channel are nottransmitted directly to the receiver 1200 b. In general, there areseveral sizes of coded blocks for the users with different wirelesschannel conditions. In the receiver 1200 b, the possible coded blocksizes are determined from predefinition or the system information suchas resource size, resource position and modulation scheme (e.g.,received from transmitter 1200 a). After the coded block sizes areknown, all the possible combinations of N_(i) and K_(i) are tested oneby one with a procedure similar to that described above for thetransmitter until the desired data is obtained. In an aspect, becausethe same predefined table for mapping (N_(i), K_(i)) into δ_(i) isapplied for both transmitter and receiver, the position set ofinformation bits obtained in transmitter is substantially identical tothat in receiver. In this way, the received signal is decoded correctlyand control data is recovered.

In an aspect, optimum performance may be obtained based on the abovedescribed procedures for constructing polar codes as the optimumconstruction SNR is predefined for each pair (N_(i), K_(i)).

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Further, somesteps may be combined or omitted. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase, for example, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, forexample the phrase “X employs A or B” is satisfied by any of thefollowing instances: X employs A; X employs B; or X employs both A andB. In addition, the articles “a” and “an” as used in this applicationand the appended claims should generally be construed to mean “one ormore” unless specified otherwise or clear from the context to bedirected to a singular form. A phrase referring to “at least one of” alist of items refers to any combination of those items, including singlemembers. As an example, “at least one of: a, b, or c” is intended tocover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combinationwith multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c,a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering ofa, b, and c).

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed as a means plus functionunless the element is expressly recited using the phrase “means for.”

1. A method for decoding a polar code by a receiver, comprising:receiving a coded block of data generated by polar encoding; determiningat least one set of parameters corresponding to the data, and a set ofsorting indices corresponding to bits of the data based on the set ofparameters, the set of sorting indices indicating a position set of thebits of the data; and decoding the received coded block of data based atleast on the set of parameters and the set of sorting indices to obtaindecoded data.